Linux Command Line and Shell Scripting Bible, 4th Edition

CHAPTER 23Working with Alternative Shells

IN THIS CHAPTER

• Understanding the Dash shell
• Programming in the Dash shell
• Introducing the zsh shell
• Writing scripts for zsh

Although the Bash shell is the most widely used shell in Linux distributions, it's not the only one. Now that you've seen the ins and outs of the standard Linux Bash shell and what you can do with it, it's time to examine a few other shells available in the Linux world. This chapter describes two other popular shells that you may run into in your Linux journey and shows how they differ from the Bash shell.

Considering the Dash Shell

The Debian Linux distribution, like many of its derivatives, such as Ubuntu, uses the Dash shell as a replacement for the standard Linux Bash shell. The Dash shell has had an interesting past. It's a direct descendant of the ash shell, a simple copy of the Bourne shell available on Unix systems (see Chapter 1, “Starting with Linux Shells”). Kenneth Almquist created a small-scale version of the Bourne shell for Unix systems and called it the Almquist shell, which was then shortened to ash. This original version of the ash shell was extremely small and fast but lacked many advanced features, such as command-line editing and history features, making it difficult to use as an interactive shell.

The NetBSD Unix operating system adopted the ash shell and still uses it today as the default shell. The NetBSD developers customized the ash shell by adding several new features, making ...